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    <head>
      <base href="https://bugs.llvm.org/">
    </head>
    <body><table border="1" cellspacing="0" cellpadding="8">
        <tr>
          <th>Bug ID</th>
          <td><a class="bz_bug_link 
          bz_status_NEW "
   title="NEW - Clang incorrectly rejects default construction of union with nontrivial member"
   href="https://bugs.llvm.org/show_bug.cgi?id=49072">49072</a>
          </td>
        </tr>

        <tr>
          <th>Summary</th>
          <td>Clang incorrectly rejects default construction of union with nontrivial member
          </td>
        </tr>

        <tr>
          <th>Product</th>
          <td>clang
          </td>
        </tr>

        <tr>
          <th>Version</th>
          <td>trunk
          </td>
        </tr>

        <tr>
          <th>Hardware</th>
          <td>PC
          </td>
        </tr>

        <tr>
          <th>OS</th>
          <td>Windows NT
          </td>
        </tr>

        <tr>
          <th>Status</th>
          <td>NEW
          </td>
        </tr>

        <tr>
          <th>Severity</th>
          <td>enhancement
          </td>
        </tr>

        <tr>
          <th>Priority</th>
          <td>P
          </td>
        </tr>

        <tr>
          <th>Component</th>
          <td>C++2a
          </td>
        </tr>

        <tr>
          <th>Assignee</th>
          <td>unassignedclangbugs@nondot.org
          </td>
        </tr>

        <tr>
          <th>Reporter</th>
          <td>mschellenbergercosta@googlemail.com
          </td>
        </tr>

        <tr>
          <th>CC</th>
          <td>blitzrakete@gmail.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
          </td>
        </tr></table>
      <p>
        <div>
        <pre>Consider the following valid TU:

```cpp
struct TriviallyConstructible {};
struct BadNontrivialClass {
    BadNontrivialClass() {}
};

union U {
    TriviallyConstructible first{};
    BadNontrivialClass second;
};

U u;
```

Currently clang rejects this with:

```
<source>:11:3: error: call to implicitly-deleted default constructor of 'U'
U u;
  ^
<source>:8:24: note: default constructor of 'U' is implicitly deleted because
variant field 'second' has a non-trivial default constructor
    BadNontrivialClass second;
```

However, according to the standard
(<a href="https://eel.is/c++draft/class.union#general-4">https://eel.is/c++draft/class.union#general-4</a>) the member initializer of
`first` makes this a valid construct.</pre>
        </div>
      </p>


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